FIXED - Hotend stops at 192c

[mhackney]

20°C (68°F) is a reasonable room temperature but you already knew the thermistor was reasonable at RT. I still think you need to measure it at 100°C in boiling water to determine if it works properly over that range (or identify a mislabeled thermistor, etc).

Also, how do you have the thermistor mounted in your hot end? Maybe a photo would help us.

[calabus]

It is mounted in the head with Ultra Copper RTV. I have the E3D head (I think you have one or one very similar). I was very careful to not get it on the glass bulb. The leads were shielded with clearish plastic protectors. I even put a tiny bit of RTV between the shielded leads at the bead to ensure no accidental short. I let that dry then slid the thermistor into the head and sealed with a light coat of RTC on the head. Maybe it isn't seated well in the hole? Either way I might as well pull it out and test as you said in water.

[mhackney]

Yup, I have an E3D and the Kraken (along with a few other) hot ends. The copper rtf may be conductive. If you have any on the thermistor leads it might be a problem.

The thermistor does need to be seated well or you won't get good heat transmission to it.

You've had nothing but bad luck on this! Given all of this pain and agony, you might consider biting the bullet and getting one of the screw in thermistors off eBay. Then there will be no doubt about mounting, thermal contact, etc.

[calabus]

Lol...yep this has been nothing but hell, but I kinda enjoy it? Live and learn I guess. I was actually looking at tapping a hole in the head for a set screw to hold the thermistor, but I don't think I have the skill for that and I'm not sure how viable that solution would be. Do you have any info/links in the screwin type thermistors? In the mean time I am going to slide it out and at least try the water test to confirm the wiring isn't still a problem.

[mhackney]

Screw in Thermistor - one of the best upgrades you'll make IMHO!

You will need a 2.5mm drill and a 3mm tap too. It turns out that you don't have to be persnickety on drilling the hole, even if it breaks into the nozzle hole it will be sealed by the nozzle.

[calabus]

Might give that a try. I did the water test and there is a 5 degree variance in temp from the thermistor and my probe.

[mhackney]

ok, that isn't horrible. So I suspect your wiring and/or mounting of the thermistor. It seems the thermistor itself is in the ballpark.

[Eaglezsoar]

Yup, I have an E3D and the Kraken (along with a few other) hot ends. The copper rtf may be conductive. If you have any on the thermistor leads it might be a problem.

The thermistor does need to be seated well or you won't get good heat transmission to it.

You've had nothing but bad luck on this! Given all of this pain and agony, you might consider biting the bullet and getting one of the screw in thermistors off eBay. Then there will be no doubt about mounting, thermal contact, etc.

Our first disagreement, I do not believe that the Copper RTV is conductive. Everyone thinks there is Copper in it because of its name but check the list of ingredients and see if you can find the
word copper in the list. Here is a statement from the Permatex Site :

Is the Permatex® Ultra Copper® Maximum Temperature RTV Silicone electrically conductive and does it have copper?
-
The Ultra Copper® is a silicone product and is copper in color. It does not contain any copper or other metal and it is not electrically conductive. For additional information, go to the Ultra Copper product page [hyperlink to 81878 product page] and view the TDS.

[calabus]

ok, that isn't horrible. So I suspect your wiring and/or mounting of the thermistor. It seems the thermistor itself is in the ballpark.

Well this was the bare thermistor in water and the wiring is completely new for the second time. I think wiring is fine now that I know what NOT to do when measuring resistance.

[mhackney]

Not disagreeing Eagle! I looked at the permatex site and they had no information on conductivity. Many silicones are very good insulators but they can be slightly conductive too depending on formulation. It was a stretch! Calabus' issue is very odd.

[Eaglezsoar]

Not disagreeing Eagle! I looked at the permatex site and they had no information on conductivity. Many silicones are very good insulators but they can be slightly conductive too depending on formulation. It was a stretch! Calabus' issue is very odd.

I think most of the problems are over...I can hope can't I?

[calabus]

Wish I could say the problem was resolved, but I tried another test with holding the thermistor into the hold firmly and running the temp up to about 160 then 180, 190 and then 195. It stopped again at about 190 and refused to report a temp higher than that. I measured with my probe and it seemed to be accurate up until about the 190 mark. I'll have to admit the temp probe is a bit hard to get a steady reading on, but looking at top end readings it seemed accurate. I will try a few more tests when I get home, but it looks like it is coming down to the Rambo board. I don;t know what else it could possibly be.

ps: I just happened to run into this thread late yesterday. Pretty much the exact same problem but on a different printer and board. No answer there either....
https://groups.google.com/forum/#!topic ... Y0x7q5L2YY

[Polygonhell]

This could POSSIBLY be a bad RAMBO board, there is a voltage divider on the board that basically adjusts the reading from the thermistor.
I would suggest either verifying that you get the same results from the other thermistor inputs look up the expected restistance of the thermistor at 250C and use a resistor of that value instead of the thermistor to validate the input is working as expected.
It could still be a configuration issue, or a bad thermistor, but it sounds like you've eliminated those by trying multiple resistors, and various thermistor settings in the firmware.

[mhackney]

Good insight Polygonhell. A quick test would be to try one of the other thermistor ports. You'll have to change pns.h to tell the firmware which thermistor port to use for hot end 0. In pins.h look for the RAMBo section. Then look for:

Code: Select all

#define HEATER_0_PIN   9
#define TEMP_0_PIN     0

The thermistor ports are numbered 0,1,2,3 from the top (the end with the hot end and bed connectors) down. By default, you probably have your heat bed thermistor on pin 2 so don't use that one

Your thermistor port 0 is TEMP_0_PIN to 0

To use thermistor port 1 change TEMP_0_PIN to 1
Hot Bed thermistor port 2 uses pin 2
To use thermistor port 3 change TEMP_0_PIN to 7

You'll have to move your thermistor connector to the appropriate port. Chances are good that if you have a faulty circuit on pin 0 you probably won't on the others.

[calabus]

So I changed the pins.h to use port 1. My readings you may ask? 256c at room temp. Ummmmm....no. Upload again and reset board. Ummm.... 256c again. Welp this is getting worse by the day. Decide to try for port 3. Fire it up and I now have identical readings as my bed. On port 0 I was about 2-3c off. Decide the run the head up to 160, 180, 190, 200.........210? Yep....230? You betcha! 245 maybe? DAMN STRAIGHT!

SWEET BABY JESUS IT WORKS!!!

So we now have a confirmed bad board, well at least 2 ports, but the rest are fine!! Months and months of pulling my hair out and rebuilding heads and it was the damn board the entire time. I haven't gotten out of this yet though. I have found an issue with the feed in Repetier. I have to hit it multiple times before it will actually extrude. Will have to see what happens after I calibrate and try and do a print. Might have that done tonight.

I would really like to thank you ALL for helping sort this out, especially mhackney for looking at my configs and providing the pins.h test! Eventually I would have probably ordered a new board at my cost still not knowing if that was really the problem, but now I know exactly what and which ports are hosed. I can continue using it and just replace it if i decide to use duel extruders one day, but I'm far from that day.